Composite articles are well known to provide advantages in diverse applications including, for example, body panels and other components for motor vehicles. In some applications the advantages of composite articles over metal, ceramic or other materials include weight reduction and the ability to integrate several otherwise individual parts into a single structure. Composite articles of this nature comprise reinforcement material in a polymer based resin, such as a thermoplastic or a thermoset plastic, which is moldable in a first condition but curable (for example, by cooling below the softening point in the case of a thermoplastic) to a form-stable condition. Numerous reinforcement materials are well known to those skilled in the art including, for example, chopped or continuous fibers disposed either randomly or in ordered fashion within the matrix. Exemplary composite materials include sheet molding compound (SMC), typically comprising chopped glass fibers in a thermoset resin, and bulk molding compound (BMC), typically comprising a granulated or putty-like mixture of chopped fibers in a polymer based resin.
A significant disadvantage frequently inherent in the manufacture of composite articles resides in the relatively long cycle times required especially for composite articles having large cross-sectional areas, such as thick wall sections and the like. The cycle time for such components, that is, the time required for loading composite material into a mold, plus the time required for molding and curing the resin of the composite article at least sufficiently to remove it from the mold can jeopardize the economic feasibility of the operation in some cases. Thick cross-sectional areas, such as thick wall sections and the like, as frequently occur in structural or semi-structural components or components having complex configurations, require relatively longer curing time than do thin cross-sectional components. In a typical case of a composite article comprising a thermoset resin, sufficient heat must be provided to the article to cure both the thick and thin cross-sectional areas. While the thinner areas may cure quickly, the cycle time is increased by the longer curing time required by the thicker sections. Longer cycle times may directly reduce the efficiency of the manufacturing process and increase the piece price of the component. It has long been a recognized need in the industry to reduce cycle times in the manufacture of composite articles. Even where lengthy cycle time is not a serious problem, there often is a need to better control the uniformity of resin cure or to deliberately accelerate curing in selected portions of the composite article. As disclosed and discussed below, various embodiments of the invention are addressed to one or more of these recognized needs and other advantages of the invention will be apparent to those skilled in the art of composite article manufacturing.